[RoboTeddy]

Certain kinds of misbehavior are punished. If you mine an invalid block, everyone will reject it, and you won't get any reward (you burnt electricity and hardware time for nothing). It works the same in PoS -- if you mine an invalid block, then (depending on the protocol) either your entire security deposit will be destroyed (ouch!) or no one will build atop your fork and you won't have any mining reward (same as PoW).

Block validation can only enforce certain kinds of rules, such as:

* People can only spend outputs they have the private key for

* You can't spend an output that has already been spent

* The block reward has a predetermined size

There are other kinds of rules that we don't know how to enforce yet. For example, we might want the rule, "Always create blocks with the top n transactions that offer the highest fee per byte, out of all the new transactions you've learned about". The trouble is that we don't know how to prove that a miner has learned of a transaction over the network. (Maybe there was a network partition, or maybe their internet connection died for a minute-- how can we tell between those conditions, and the case where the miner learned of but ignored a transaction?)

The "misbehaviors" listed in the article fall into this category: things we might like to make rules against, but don't know how to (or know how to, but haven't bothered yet).